Refrigerating apparatus



Feb. 23, 1943- E. k. FITZGERALD- 2,312,087

REFRIGERATING APPARATUS Filed March 8, 1941 Inventor:

Edward RFitz eTaId,

b w 6. M y Hmttorney which characterize my Patented Feb. 23, 19432,312,087 REFRIGERATING aPrAn'A'rUs Edward RhFitzgerald, Schenectady, N.Y., assignor to General Electric Company, a corporation of ,New .York

Application March 8, 1941, Serial No. 382,415

1 Claim. (01. 62-8) v My invention relates to refrigerating apparatusand particularly to devices for controlling the operation of suchapparatus.

Refrigerating machines constructed for the preservation of food-stuffscommonly comprise a thermally insulated cabinet provided with a storagecompartment and ;a cooling unit or evaporator in the upper portion ofthe compartment. The cooling unit when arranged in the upper portion ofthe compartment induces a circulation of air throughout the compartmentand maintains the articles stored therein "within; a predetermineddesired range of temperatures. It is common practice to control therefrigerating machine to maintain a predetermined range of temperaturesof the evaporator or cooling unit, this. range of temperatures beingselected so that the range of bo air temperatures resultingjherefromwill be satisfactory for the preservation of food within thecompartment. By controlling the cooling unit in this manner, it ispossible to maintain temperatures below freezing suitable for thefreezing of ice desserts and the like in the cooling unit whilemaintaining the cabinet airtemperature above freezing.

The ability of a refrigeratingmachine to maintain a predetermineddesired temperature of the changes in the temperature of the airsurrounding the cabinet; the higher the temperature of the air outsidethe cabinet, the greater is the amount of heat which passes through thecabinet walls to the air within the food compartment and the lower isthe required evaporator temperature. Various devices have been designedto pro-' vide a control of the refrigerating machine which will vary theoperation of the normal control to determine the evaporator temperaturein accordance with changes in the temperature of the air outside thecompartment.

It is an object of, my invention to provide a refrigerating apparatusincluding an improved control for maintaining a predetermined. desiredrange of temperatures within a refrigerating i compartment.

It is another object of my invention to provide a simple and improveddevice for controlling the cooling unit of a refrigerating machine tovary the eflective capacity of the unit in accordance with changes inthe temperature of the air within the compartment to be cooled.

Further objects and advantages of my'invention will become apparent asthe following description proceeds. and the features of noveltyinvention will be pointed air in a compartment to be cooled varies. without with particularity inthe claim annexed to and forming a part of thisspecification.

For abetter understanding of my invention reference may be had to theaccompanying drawing in, which Fig. 1 is a diagrammatic view of arefrigerating machine providedwith, a. \control embodying my invention;Fig. 2 is an enlarged front elevation view of the evaporator shown inFig. 1 arranged in a household refrigerating cabinet, and Fig. 3 is anenlarged perspective view of a portion of the evaporator shown in Fig.v

2 partly broken away to show the'inside of the header.

In general, the refrigerating apparatus shown in the drawing comprises arefrigerant compressor, a condenser, and an evaporatorconnectedin aclosed refrigerant circuit. The compressor is driven by an alternatingcurrent motor, the operation of which is controlled in accordance withthe temperature prevailing on the surface of the evaporator immediatelyabove the-header where the temperature responsive element of the controlis secured. The position of the control bulb on the evaporator is suchthat the temperature of the bulb depends not only on the temperature ofthe evaporator but also on the temperature of the air circulating in theupper portion of the refrigerated compartment.

Referring now to the drawing, inFig. 1 I have shown a refrigeratingmachine comprising a compressor l0 arranged to deliver compressedrefrigerant tola condenser H in which the re-. frigerant is cooled andliquefied. vLiquid refrigrefrigerant is separated from the liquid in theheader i4 and is withdrawn from the evaporator through a suction line I6and is returned to the compressor. The compressor is driven by analternating current electric motor i'l comprising a squirrel-cageinduction rotor i8 and a suitable stator including a running winding l9and a 'starting winding 20. The operation of the motor I1 is controlledby a temperature responsive switch 2| having a thermal element 22secured to the evaporator 13. The thermal element 22 comprises a bulbpartially. filled with a vaporizable liquid and arranged to actuate abellows II. to which it is connected by a tube 22a in the usual manner.move an arm 14 against the force of the spring 25 and to actuate amovable contact 20 of they control II. The contact II is moved with snapaction by operation of an over-center. spring 21. when the temperaturein the. evaporator rises above -a predetermined value, the bellows 23expands and moves a pivot point 2! of the switch overthe center line' ofthe spring I1 thereby snapping the'movable contact 2. into ita -closedThebellows Ilisarraugedto.

position and closing the circuit from one side or. alternating currentsupply lines through a re lay coil 30 and the starting winding I! to theotherside oi the supply lines. The coil picks up-an armature raising acontact bridging arm II and closing the circuit oi the starting winding2|, thereby connecting the starting and running windings in parallelacross the supply lines. The starting winding is a-split-phase windingwhich acts with the running winding I! to produce a rotating fleld andstarts the rotation of the squirrel-cage rotor is thereby starting thecompressor. As the speed of the motor increases, the

current flowing in the windings is reduced and.

as full speedis approached, the armature'oi the solenoid drops outthereby disconnecting the starting winding. The motor then continues tooperate as a single-phase induction motor.

- When the temperature of the freezing portion of the evaporator hasbeen reduced to its predetermined lower limit, the bellows 23 contractssumciently to allow the spring 25 to draw the pivot 28 over centerthereby snapping the contact 25 to its open position and stoppingoperation of the motor. g

In order that the operation of the refrigerating machine shall maintainthe evaporator temperature within its requiredrange and also main- 7tain the temperature of the air in the compartment to be cooled within apredetermined'range,

the bulb 22 0! the thermostatic control is secured to the evaporator ina position such that its tema perature depends not only on thetemperature or the evaporator but also on the temperature of the aircirculating in'the upper portion of the compartment to beicooled."I'hisarrangement of the thermal element 22 is clearly shown in Figs. 2and 3. In Fig.2 Ihaveshown the evaporator II provided with a door 32 andarranged header. The wall 31 is bent to form a flange 38 by which theevaporator is secured to the top oi the cabinet. The control II ismounted adjacent the top of the evaporator on a suitable panel 39 and isprovided with an adjusting knob l0 which is connected in the usualmanner (not shown in the drawing) to'vary the eil'ective forceoi thespring 25.

As clearly shown in Fig.:,3 the evaporator l3 is composed 01 two sheetmetal portions ll and 42 secured together iniace engagement and providedwith suitable indentations forming the liquid reirigerant circulatingconduits I! and the two halves oi the cylindricalheader Il The sheetmetal portion 4i isv bent around theedges of a sheet 42 as indicated at43 and thetwb sheets.v

are secured together around their edges and bethe asiaosr tween thepassages It and around the headerbi welding or in anyother suitablemanner. The flange II at the top oi-the vertical wall of the evaporatoris provided with suitable holes 44 so. that the evaporator may besecured to the topwall oi the refrigerator cabinet. A strip oi cork orother insulating material N is placed between the flange 8| andthe topwall of the refrigerator The upright portion or the evaporator wallabove the header I4 is in path of relatively warm air circulatingthrough the upper portion of the compartment to be cooled and itstemperature tends to vary with the changes in the temperature of theair; the operation of the evaporator ll liquid refrigerant is maintainedabove the ends oi the conduits II to a level approximately. hali'fllling the header. and due to the absorption of heat. the liquidrefrigerant boils and the vapor passes up through the conduit; to thesurface of the liquid in the header; In order to prevent the splashingoi refrigerant in and around the'suction line I! which communicates withthe evaporator within the upper portion of the header, there is provideda baillell extending'longitudinally'within the header at an'angle'between the upper ends 01' theconduit" es I5 and the opening of thesuction line ",thebaiiie ein s ured in pla e v-suitabie-upperrand lowerflanges 41 and ll, respectivelyg and by tabs 49 on endwalls ill. The endwalls are provided with narrow upwardly eirtendingslots 5| which providecommunication'betwe'enthe header and the space within the bailieboth'iab'ovennd below the leveloi' liquid reirigerant'in the header. Thebaflle 48 prevents thesplashingoi' liquid rel'rigerant against the topoi the header. within the conflnes of 'thebaflle; and"! arrange the.-

bulb 22 immediately above the bailie so'that liquid refrigerant is notsplashed againsttheu'waliof" the evaporator adjacent the bulb; and thebulb is therefore not subject to fluctuations'of -tempera-' ture due tothe splashingoi refrigerant "in its vicinity.

' I prei'er'to construct theevaporator stainless steel which is amaterial 01 relatively lo thermal conductivity as compared with othermztals as copper-and aluminum; The flow, as heat through the walloi'xthe evaporator 'ls impeded and sincethebulbrfliis arrangedin lcontrols additional i. mechanisms. 1.

position \such. that liquid"- refrigerantv can, not

strike-the wall of the evaporator immediately ads Jacent the bulb, thereis a substantialdrop or gradient in temperature from theaw'allvl'l-around the header oi the evaporator. to the portion of the headerin contact with liquid refrigerants The bulb 22 is thereforeresponsiveto. a temperature which is intermediate-that oi'rthe walllland the coldest orireez g portion of the. evaporator and this temperaturis influenced by the rise of temperature oi thea r flowing over thewalll'l-and the temperature (it the liquid reirigerantginthe evaporator;it follows that, should .;the',-temperature' of the air-in ecabinetvrise' and thereby increase the temperaureoi.-.the*wnll-vlfl',-.the.evaporator will operate until'fiitstemperature is reduced sufllciently to overcome thisrise o! temperatureand cool the bulb 21 to the temperature at which it will shut oil-therefrigerating machine. a 1 i s v The arrangement of the-temperaturerespon sive bulb and of the header of the'evaporator in the manner justdescribed makes it possible to provide compensation 01118171118 box airtemperatures without the necessity ofcomplicated such reiore and it isreadily apparent that I have provided a simple and effective controldevice for refrigerating apparatus whereby the predetermined range oftemperatures in the compartment to be cooled may be maintainedregardless of changes of temperature outside the compartment.

While I have described my invention in connection with a householdrefrigerator, other applications will be apparent to those skilled inthe art; I do not, therefore, desire my invention to be limited to theparticular construction shown and described and I intend in the appendedclaim to cover all modifications'within the spirit and scope of myinvention.

What I claim as new and desire to secure by Letters Patent of the UnitedStates is:

and a depending refrigerant circulating conduit therein, said wallhaving an upright portion above said header for securing said evaporatorin said compartment, battling means arranged within said header forproviding a quiet zone of liquid refrigerant therein, means forsupplying refrigerant to and ior withdrawing refrigerant from saidevaporator, and a control means including a temperature responsiveelement secured to said evaporator adjacent said upright wall andimmediately above said quiet zone for controlling the operation of saidrefrigerant supplying and withdrawing means, the operation of saidevaporator providing a substantial gradient between the temperature ofsaid upright portion and the temperature of said freezing portion, thetemperature of said element lying along said gradient intermediate saidtemperatures whereby said control provides operation of said evaporatorto maintain the temperature thereof sufiiciently low to compensate forincreases in the temperatureof the air in said compartment.

EDWARD R. FITZGERALD.

